Serum Free Light Chain Immunoassay (kappa and lambda)
This test measures the free kappa and lambda light chains in your blood, which are small protein fragments produced by plasma cells. It helps identify conditions affecting plasma cells, such as multiple myeloma or other monoclonal gammopathies.
["This test helps diagnose and monitor certain blood disorders linked to abnormal protein production."]
Key facts at a glance
- LOINC
- 108865-7
- Short code
- RF IgM Msmt Ser
- Synonyms
- RF IgM Msmt Ser
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 86430
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your healthcare provider may order this test if you have symptoms like unexplained fatigue, frequent infections, or unexplained bone pain. It may also be used to monitor treatment progress in people with known plasma cell disorders or to screen for conditions like multiple myeloma or Waldenström macroglobulinemia.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into a vein in your arm to draw blood. This usually takes a few minutes and is generally not painful. Avoid eating or drinking for a short time before the test if instructed.
What the Test Results Mean
Results show the levels of free kappa and lambda light chains. Elevated levels can indicate conditions like multiple myeloma, where abnormal plasma cells produce too many light chains. Your provider will interpret the results in the context of your symptoms and medical history.
Common Conditions Monitored
This test is often used to diagnose or monitor multiple myeloma, a cancer of plasma cells, or other conditions such as monoclonal gammopathy of undetermined significance (MGUS) and Waldenström macroglobulinemia.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormally high levels of free light chains can signal plasma cell disorders. For example, multiple myeloma often shows an imbalance between kappa and lambda chains. Your provider will use these results alongside other tests and clinical findings to guide diagnosis and treatment planning.
Short name
Free Light Chain Test
Frequently asked questions
What causes abnormal light chain levels?
How often will I need this test?
Can diet or medications affect this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy